Drug-induced death of leukaemic cells after G2/M arrest: higher order DNA fragmentation as an indicator of mechanism.
Many reports have documented apoptotic death in different cell types within hours of exposure to cytotoxic drugs; lower drug concentrations may cause cell cycle arrest at G2/M and subsequent death, which has been distinguished from 'classic' apoptosis. We have analysed etoposide-induced cell death in two lymphoblastoid T-cell lines, CCRF-CEM and MOLT-4, specifically in relation to DNA cleavage as indicated by pulse-field gel and conventional electrophoresis. High (5 microM) concentration etoposide causes 50-kb cleavage of DNA that occurs at the same time as apoptotic morphology and internucleosomal cleavage. At lower concentrations (0.5-0.05 microM), sequential change may be discerned with altered gene expression being similar to that at high dose, but preceding cell cycle arrest and 50-kb cleavage. These last changes, in turn, clearly precede internucleosomal fragmentation of DNA, vital dye staining and morphological evidence cell death. The pattern of higher order fragmentation constitutes a sensitive indicator of commitment to cell death in these cells. Morphological evidence of cell death is associated with internucleosomal fragmentation in one of the lines, but the pattern of 50-kb DNA cleavage provides the clearest evidence of commonality in death processes occurring at low and high drug concentration.
Sleiman
R J
RJ
Children's Cancer Research Institute, University of New South Wales, Sydney Children's Hospital, Australia.
Catchpoole
D R
DR
Stewart
B W
BW
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D004396:Coloring Agents; D053938:DNA Fragmentation; D004273:DNA, Neoplasm; D016521:Electrophoresis, Gel, Pulsed-Field; D005047:Etoposide / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000473:pathology*; D008938:Mitosis / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D014343:Trypan Blue; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000972:Antineoplastic Agents, Phytogenic; D004396:Coloring Agents; D004273:DNA, Neoplasm; D005047:Etoposide; D014343:Trypan Blue